Crucial Role for the Myelin‐associated Glycoprotein in the Maintenance of Axon‐Myelin Integrity

Abstract

It has recently been shown that mice deficient in the gene for myelin‐associated glycoprotein develop normal myelin sheaths in the peripheral nervous system. Here we report that in mutant mice older than 8 months the maintenance of axon‐myelin units is disturbed, resulting in both axon and myelin degeneration. Morphological features include those typically seen in human peripheral neuropathies, where demyelination‐induced Schwann cell proliferation and remyelination lead to the formation of so‐called onion bulbs. Expression of tenascin‐C, a molecule indicative of peripheral nerve degeneration, was up‐regulated by axon‐deprived Schwann cells and regenerating axons were occasionally seen. Myelin‐associated glycoprotein thus appears to play a crucial role in the long‐term maintenance of the integrity of both myelin and axons.